This invention relates to a projection exposure apparatus and a device manufacturing method. More particularly, the invention is concerned with a projection exposure apparatus having a function for correcting or reducing a change in optical characteristic of a projection optical system due to a change in atmospheric pressure, and with a device manufacturing method for producing devices such as semiconductor chips, liquid crystal devices, image pickup devices or magnetic sensors, for example, by use of such a projection exposure apparatus.
Generally, a projection optical system of a projection exposure apparatus includes refractive optical elements such as, typically, a lens. Due to a change in pressure of air between optical elements of the projection optical system resulting from a change in atmospheric pressure, the refractive index of the air itself changes, which causes a change in relative refractive index of a glass material and the air. This results in a change in optical characteristic of the projection optical system, such as focus position, projection magnification, distortion aberration, spherical aberration, coma aberration, astigmatism, or curvature of field, for example.
Japanese Laid-Open Patent Application, Laid-Open No. 123238/1989 and No. 305034/1996 show a projection exposure apparatus wherein all refractive optical elements used in the projection optical system are made of the same glass material (fused silica), and wherein, by changing the wavelength of KrF excimer laser exposure light (wavelength of 248 nm), the refractive index of the glass material is changed to correct a change in relative refractive index of the glass material and the air due to a change in atmospheric pressure, by which all the optical characteristics such as described above are corrected.
However, in a case where, like a projection exposure apparatus having an ArF excimer laser (wavelength 193 nm), a very fine device pattern should be projected on a resist of a substrate and, to this end, two or more different glass materials such as fused silica and fluorite are used in refractive optical elements of the projection optical system for correction of chromatic aberration. Since these glass materials have different refractive indices and dispersions, changing the wavelength of laser light to change the refractive indices of the glass materials does not contribute to correction of a change in relative refractive index between the glass material and the air due to a change in atmospheric pressure, with respect to all the glass materials used. Thus, good correction of a change in optical characteristic such as described above, ends in failure. Japanese Laid-Open Patent Application, Laid-Open No. 305034/1996, mentioned above discusses a projection optical system having two or more glass materials, simply.
It is an object of the present invention to provide a projection exposure apparatus by which a change in optical characteristic of a projection optical system having refractive optical elements of two or more glass materials, due to a change in atmospheric pressure, can be reduced.
It is another object of the present invention to provide a device manufacturing method using such a projection exposure apparatus.
It is a further object of the present invention to provide a projection exposure apparatus by which a change in optical characteristic of a projection optical system having refractive optical elements of two or more glass materials, due to a change in atmospheric pressure, can be substantially corrected (reduced to zero or to such a low degree that pattern resolution is not affected thereby).
It is a yet further object of the present invention to provide a device manufacturing method using such a projection exposure apparatus just above.
In accordance with a first aspect of the present invention, there is provided a projection exposure apparatus for projecting a pattern of a mask, illuminated with exposure light, onto a substrate through a projection optical system, characterized by means for changing the wavelength of exposure light to reduce a change in optical characteristic of the projection optical system due to a change in atmospheric pressure, wherein said projection optical system has plural refractive optical elements made by use of two or more glass materials, wherein interspaces of the refractive optical elements are filled with gaseous fluids of a pressure the same as or substantially the same as atmospheric pressure, and wherein a gaseous fluid in at least one interspace differs in refractive index from a gaseous fluid in at least one of the remaining interspaces.
In accordance with a second aspect of the present invention, there is provided a projection exposure apparatus for projecting a pattern of a mask, illuminated with exposure light, onto a substrate through a projection optical system, characterized by means for changing the wavelength of exposure light to substantially correct a change in optical characteristic of the projection optical system due to a change in atmospheric pressure, wherein said projection optical system has plural refractive optical elements made by use of two or more glass materials, wherein interspaces of the refractive optical elements are filled with gaseous fluids of a pressure the same as or substantially the same as atmospheric pressure, and wherein a gaseous fluid in at least one interspace differs in refractive index from a gaseous fluid in at least one of the remaining interspaces.
In accordance with a third aspect of the present invention, there is provided a projection exposure apparatus for projecting a pattern of a mask, illuminated with exposure light, onto a substrate through a projection optical system, characterized by detecting means for detecting a change in atmospheric pressure and wavelength changing means for changing the wavelength of exposure light in accordance with an output of said detecting means, wherein said projection optical system has plural refractive optical elements made by use of two or more glass materials, wherein interspaces of the refractive optical elements are filled with gaseous fluids of a pressure the same as or substantially the same as atmospheric pressure, and wherein a gaseous fluid in at least one interspace differs in refractive index from a gaseous fluid in at least one of the remaining interspaces.
In accordance with a fourth aspect of the present invention, there is provided a projection exposure apparatus for projecting a pattern of a mask, illuminated with exposure light, onto a substrate through a projection optical system, characterized by means for changing the wavelength of exposure light to reduce a change in optical characteristic of the projection optical system due to a change in atmospheric pressure, wherein said projection optical system has plural refractive optical elements made by use of two or more glass materials, wherein interspaces of the refractive optical elements are filled with inert gaseous fluids of a pressure the same as or substantially the same as atmospheric pressure, and wherein a gaseous fluid in at least one interspace differs in refractive index from a gaseous fluid in at least one of the remaining interspaces.
In accordance with a fifth aspect of the present invention, there is provided a projection exposure apparatus for projecting a pattern of a mask, illuminated with exposure light, onto a substrate through a projection optical system, characterized by means for changing the wavelength of exposure light to substantially correct a change in optical characteristic of the projection optical system due to a change in atmospheric pressure, wherein said projection optical system has plural lens elements made by use of two or more glass materials, wherein interspaces of the lens elements are filled with gaseous fluids of a pressure the same as or substantially the same as atmospheric pressure, and wherein a gaseous fluid in at least one interspace differs in refractive index from a gaseous fluid in at least one of the remaining interspaces.
In accordance with a sixth aspect of the present invention, there is provided a projection exposure apparatus for projecting a pattern of a mask, illuminated with exposure light, onto a substrate through a projection optical system, characterized by detecting means for detecting a change in atmospheric pressure and wavelength changing means for changing the wavelength of exposure light in accordance with an output of said detecting means, wherein said projection optical system has plural lens elements made by use of two or more glass materials, wherein interspaces of the lens elements are filled with inert gaseous fluids of a pressure the same as or substantially the same as atmospheric pressure, and wherein a gaseous fluid in at least one interspace differs in refractive index from a gaseous fluid in at least one of the remaining interspaces.
In accordance with a seventh aspect of the present invention, there is provided a device manufacturing method, comprising the steps of:
applying a resist to a wafer; exposing the wafer resist with an image of a device pattern by use of any of the exposure apparatuses as recited above; and developing the resist having been sensitized by the device pattern image.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.